1. Field of the Invention
The present invention relates to a pipe joint structure of a high pressure fuel accumulation device applicable to an accumulation type fuel injection system.
2. Description of Related Art
Conventionally, an accumulation type fuel injection system is known, in which high pressure fuel is accumulated in an accumulation device so called a common rail and the high pressure fuel thus accumulated is injected from respective injectors to respective cylinders of a diesel engine. The conventional accumulation type fuel injection system has a drawback in that, since pressure of the fuel accumulated in the common rail is extremely high (for example, about 150 Mpa), if pressure pulsation occurs on injecting the fuel from one of the injectors, the pressure pulsation is likely to cause pressure variation in the common rail so that respective fuel injection amount and injection timing of the other injectors are fluctuated.
To cope with this drawback, for example, JP-P-3355699 discloses a prior art for reducing the pressure pulsation in such a manner that a throttle 120 (an orifice) is provided at a bottom of a pipe joint 110 formed in a common rail 100, as shown in FIG. 8.
According to a structure shown in FIG. 8, since the throttle 120 is positioned at a bottom of the pipe joint 110 to which a high pressure pipe 130 is connected, fabrication of the throttle 120 is a troublesome work and it is rather difficult to form the throttle 120 with accurate dimension, resulting in higher fabrication cost.
Further, since the throttle 120 is formed directly in a main body of the common rail 100, it is troublesome to mass-produce plural models of the common rails 100 in which respective models thereof have substantially uniform main bodies but have different diameters of the throttles. That is, it is very difficult to standardize fabrication of the common rail 100, resulting in higher manufacturing cost of the high pressure fuel accumulation device.